NEWS
WELL ABANDONMENT AND DECOMMISSIONING
DECOMMISSIONING AND PLUGGING OF ABANDONED WELLS
We have reviewed several well abandonment procedures and recommendations from various provincial and federal government agencies. Wells fall into one of two categories, small diameter drilled wells and large diameter bored wells. The procedures are different for these two types of wells. Our proposed protocol and specifications are as follows. Please check with authorities in your area before abandoning any water well as there may be different requirements.
A.) Drilled Wells
1.) Remove any piping and pumping equipment from the well.
2.) Measure and record the water level, the total well depth, the casing diameter, and the casing type.
3.) Chlorinate the well to a level of at least 200 ppm.
4.) i.) Using Bentonite Chips: Recommended for very shallow wells only!
. Fill the entire well with EconoPlug coarse bentonite chips. EconoPlug is a sealing material that is approved for sealing wells and bore holes.
. Be sure to follow instructions when using the bentonite chips. Calculate the well volume and determine the volume of chips that will be required to plug the well. All of this material must flow into the well. Add the bentonite very slowly to prevent bridging making sure all of the bentonite goes down the well.
ii.) Using Bentonite Grout:
. While it is possible to use bentonite chips for sealing shallow drilled wells, there is a possibility of bridging occurring resulting in voids or open spaces in the water well casing. The smaller the diameter of the well or the deeper the well, the more likely the chance for bentonite chips to bridge. The standard recommended procedure is to use a bentonite grout/cement mixture that is pumped into the well. The well should be filled with this grout mixture from the bottom up through a tremie pipe displacing any water from the well. This method of well decommissioning requires specialized equipment and therefore an experienced contractor should be contacted.
5.) Excavate around the well and cut off the casing at 2.0 to 3.0 meters below ground level. Fill, compact and mound the excavation with native clay material.
6.) Record the location to the closest building or landmark, and record a GPS location.
B.) Bored Wells
1.) Remove any piping and pumping equipment from the well.
2.) Measure and record the water level, the total well depth, the casing diameter, the casing type.
3.) Chlorinate the well to a level of at least 200 ppm.
4.) Add enough coarse bentonite chips to place a 0.3 meter plug in the bottom of the well.
5.) Fill the well with a clean locally available sandy material free of organics to a level 3.0 meters from ground surface. Add a second 0.3 meter bentonite plug.
6.) Excavate around the well and cut off the casing at 2.0 to 3.0 meters below ground level. Fill the balance of the well with clay and tamp. Compact and mound the excavation with native clay material.
7.) Record the location to the closest building or landmark, and record a GPS location.
8.) Deep bored wells may require additional bentonite plugs depending upon the subsurface geology at their location.
Summary
There may be special situations where different procedures are required. It is important to take the well decommissioning process seriously as we are protecting our most precious resource on this planet - water.
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